using System;

public class Program

{

    public static void Main()

    {

        var opt1 = new Options();

        var fac = ConnectionFactory.GetInstance().CreateConnection(opt1);

        Console.WriteLine("ConnectionFactory options: " + opt1.ConnectionString);

        var opt2 = new Options();

        fac = AdvancedConnectionFactory.GetInstance().CreateConnection(opt2);

        Console.WriteLine("AdvancedConnectionFactory options: " + opt2.ConnectionString);

    }

}

​

public abstract class ConnectionFactoryBase<T> where T : class, new()

{

    private static T _instance;

​

    public static T GetInstance()

    {

        if(_instance == null)

            _instance = new T();

        return _instance;

    }

    public abstract Connection CreateConnection(Options options);

​

    protected void AddTemplate(Options options)

    {

        // do some templating stuff on the connection string

        options.ConnectionString = "some templated string";

        Console.WriteLine("AddTemplate");

    }

}

​

public class ConnectionFactory : ConnectionFactoryBase<ConnectionFactory>

{

    public override Connection CreateConnection(Options options)

    {

        return IntermediateMethod1(options);

    }

​

    private Connection IntermediateMethod1(Options options)

    {

        AddTemplate(options);

        return new Connection(options);

    }

}

​

public class AdvancedConnectionFactory : ConnectionFactoryBase<AdvancedConnectionFactory>

{

    public override Connection CreateConnection(Options options)

    {

        return CreateAdvancedConnection(options);

    }

    public AdvancedConnection CreateAdvancedConnection(Options options)

    {

        AddTemplate(options);

        return new AdvancedConnection(options);

    }

}

​

public class Connection

{

    public Connection(Options options) {}

}

​

public class AdvancedConnection : Connection

{

    public AdvancedConnection(Options options)

        :base(options) {}

}

​

public class Options

{

    public string ConnectionString;

    public Options() {}

}